Method and device for detecting a break in knitting needles



June 17, 1969 TATSUYA KAWAKAMI ETAL 3,449,931

METHOD AND DEVICE FOR DETECTING A BREAK IN KNITTING NEEDLES Filed Sept. 27, 1966 Sheet I of s Eye .6 F bg.1 'f'/ 9' MUM H 11 i H H June 17, 1969 TATSUYA KAWAKAMI ETAL 3,449,931

METHOD AND DEVICE FOR DETECTING A BREAK IN KNITTING NEEDLES Filed Sept. 27, 1966 Sheet & of 3 E sy- June 17, 1969 TATSUYA KAWAKAMI ET L 3,449,931

METHOD AND DEVICE FOR DETECTING A BREAK IN KNITTING NEEDLES Filed Sept. 27, 1966 Sheet ,3 of 3 United States Patent 3,449,931 METHOD AND DEVICE FOR DETECTING A BREAK IN KNITTING NEEDLES Tatsuya Kawakami, Tokyo, and Noboru Aisaka, Yokohama, Japan, assignors to Agency of Industrial Science & Technology, Tokyo, Japan, a corporation of Japan Filed Sept. 27, 1966, Ser. No. 582,331 Claims priority, application Japan, Oct. 1, 1965, to/60,104; Dec. 13, 1965, 40/76,615 Int. Cl. D04b 35/10 US. Cl. 66-157 4 Claims ABSTRACT OF THE DISCLOSURE An apparatus for detecting a broken needle and stopping the knitting operation of a circular knitting machine comprising means for detecting the force on a needle disposed in a position where the knitting needle is drawn in slightly while the butt thereof is sliding and passing during knitting, a force measuring strain gauge means for measuring the force detected by the detecting means, means for converting the measured force into an electrical signal, and circuit means for shutting off the circular knitting machine when the force on a knitting needle is zero.

The present invention relates to a method and apparatus for detecting a break in a needle during knitting operations and for stopping the knitting operation.

Among the knitting defects to be developed in a knitting operation, the one most seriously affecting the product is the knitting defect caused by a break in the needle.

In some circular knitting machines, a device for detecting a break in a needle is attached only at a cylinder needle, but a device for detecting a break in a needle has not been developed at all for the dial needles.

It is one object of the present invention to provide a device for solving basically the problem of detecting a break in a needle during a knitting operation by a circular knitting machine, thereby offering a method and apparatus for preventing knitting defects occurring due to breaks in the needles.

It is another object of the present invention to provide a device wherein a broken needle may be detected by utilizing the force applied to the knitting needle by the knitting yarn during the knitting operation, and the device may be attached easily to a conventional circular knitting machine.

It is yet another object of the present invention to provide in a knitting machine, such as a circular interlock knitting machine having a three step stitch cam means, irrespective to the action for selecting a needle, by attaching to each one, a detecting device of the present invention to the cylinder side and the dial side, whereupon all broken needles can be watched, and whereupon the quality of the product can be improved and production increased. The device of the present invention can be manufactured at a low expense without contributing to the high cost of the product.

With these and other objects in view, which will become apparent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawings, in which:

FIGURE 1 is a side view of a knitting needle of a knitting machine;

FIG. 2 is a side view of a broken knitting needle;

FIG. 3 is a side view of a stitch cam having the device for detecting broken needles according to the present invention;

3, 1,49,93 l Patented June 17, 1969 "Ice FIG. 4 is an enlarged side view of the essential part of the stitch cam shown in FIG. 3;

FIG. 5 is a side view of a stitch cam having the detecting device shown in FIG. 3, showing the detecting device displaced to another position;

FIG. 6 is a perspective view showing the movement of the knitting needles in the circular knitting machine;

FIG. 7 is a partial perspective view of another embodiment showing the detecting device of the present invention attached to the needle cylinder;

FIG. 8 shows one example of a logic circuit for stopping the knitting operation;

FIG. 9 is a signal sequence chart for FIG. 8;

FIG. 10 is another embodiment of the present invention showing the detecting device attached vertically to the knitting needles; and

FIG. 11 is another embodiment showing the present detecting device attached in parallel to the knitting needles.

Referring now to the drawings, and more particularly to FIGS. 1 to 5, a part of a stitch cam 6 is removed and replaced by an element 7 for detecting the force developed in the needle during knitting. Accordingly, the stitch cam 6 is reproduced and at the same time the element 7 is provided with strain gauges 8 for measuring the force. This serves to detect the end of the broken needle, so that the variation of the force developed by the broken needle during knitting can be detected.

Namely, as shown in FIG. 1, when the knitting needle 1 hangs a yarn 4 and drops it into a loop 5 of the previous stitch, the butt 3 of the knitting needle 1 slides on the surface of the stitch cam 6, and the drawing of the knitting needle completes one cycle of knitting action.

At this time, when the knitting needle is normal, the force due to knitting is increased and transmits a force to the detecting element 7, and the force is detected by gauges 8.

The gauge used in the present invention is a gauge for measuring the strain of a resistance wire or semi-conductor using a two-gauge method.

The force to be exerted in the needle during knitting is greatest when the needle latch 2 passes through the loop 5 of the previous stitch and when it draws in the supplied yarn 4 thereafter. This force is about from 30 grams to a few hundred grams and is defined as the knitting force in the present invention.

The face of the element 7 for detecting the knitting force is attached at a position on the stitch cam face where the butt 3 of the needle 1 is situated at the moment when the needle generates the knitting force.

In FIG. 3, the detecting element 7 is at the lowest part of the stitch cam 6, and constitutes the most general case, but of course the case can be considered in which it is positioned at the intermediate end of the cam 6 as shown in FIG. 5.

On the one hand, the form of a broken needle is such that the hook parts break off as shown in FIG. 2. Such a broken needle does not draw in the yarn to be supplied, so that no force is transmitted to the detecting element 7 resulting in no detection of force.

Any force detected is converted into an electrical signal; and using the circuit, when there is no force, a driving electrical source switch is actuated for stopping the knitting operation.

Further, in FIG. 4, the surface of the stitch cam 6 is formed in such a way that the edge 9 of the cam 6 provides a slight step so that the butt 3 may pass safely.

Referring now again to the drawings, and in particular to FIGS. 6 to 11, a knitting action is carried on by the up and down motion of the knitting needles 1 operated by raising cams 12 and stitch cams 13 which are arranged at a predetermined distance on cylinder 10 or dial 11.

In the embodiment previously described, the stitch cam itself has the device for detecting the broken needle encased therein, but now the detecting device attached to the cylinder side willbe explained.

In a knitting repose section 14 in which the needles are travelling between two stitch cams '13, the needles normally are disposed in such a position that they hang the new stitches at the hook part. In this section 14, the detecting device is attached to a supporting table 17 which is fixed to the circular knitting machine. The detecting element 15 of the detecting device is arranged inclined relative to the butt 3 of the knitting needles 1 which are moving in a row. The butt 3 is passed sliding along the detecting element 15, and at this time by drawing in the needle a little, the force to be raised in the stitch can be detected.

This force is different from the knitting force, and it is the force of the stitch occurring when a perfectly knitted stitch is subjected to further tension, and attains from 50 grams to a few hundred grams. This is called the stitch force in the present invention.

The gauges 16 used for measuring the force given to the detecting element 15 are the same as in the embodiment described before, but though either of them is used, the stitch force is zero when the hook part of the needle breaks off.

By observing the existence or non-existence of this force, a breaking of the needle can be detected easily.

Further, by the same method as described above, the force can be measured by attaching the detecting device to the side of the dial 11, and thereby any dial needle breakage, which hitherto has been regarded as diflicult to ascertain, can be detected easily.

In order to obtain two conditions of existence and nonexistence of the force imparted to the cylinder needles and dial needles, two detecting devices are attached to the respective sides. From these signals, through the logic circuit as shown in FIG. 8, when a needle on either side is broken, the switch controlling the driving electrical source is actuated, and the knitting operation is stopped.

Referring now again to the drawings, and in particular to FIGS. 8 and 9, one embodiment of the logic circuit for stopping the knitting operation is illustrated.

Let the output on the side of the cylinder and the output on the side of the dial be set input S and reset input R respectively. Then, when both the cylinder needles and the dial needles are normal, a pulse of S and R are generated alternately.

Now, suppose that the dial needle is broken. Then the reset pulse R disappears. At this time, an output Z of flip-flop 18 is produced. This output Z and the set input S are passed through AND-gate 19, whereby an output pulse A is obtained, so that when this pulse A is put into flip-flop 21 through OR-gate 20, an output Z is produced. When this output Z is sent to relay 22, the driving electrical source is out 011 and the knitting operation is stopped.

Further, when the cylinder needle is broken, quite the same as described above, the output Z of the flip-flop 18 operates.

A push button switch SW is actuated when restarting for resetting the flip-flop 21.

Referring now again to the drawings, and more particularly to FIGS. 10 and 11 showing other embodiments of the detecting device, when the butt 3 of the knitting needles 1 are positioned in the knitting repose section 14, they are not necessarily on a straight line and sometimes they are in a staggered state, alternately.

Further, in the circular knitting machine over 18 gauge, the needle space becomes under 1.4 mm., so that sometimes the stitch forces cannot be detected accurately only by the detecting element 15a or 15b. In this case, the staggered state of the butts 3 may preferably be corrected by the auxiliary heads 15a or 15'b, and then the detecting element 15a or 15b may be drawn in.

FIG. 10 shows the detecting device attached vertically to the direction of the knittingneedles, and FIG. 11 shows it attached in parallel to the direction of the knittin needles. 7

Even when the detecting element having no auxiliary head is to be attached, it may be carried in practice by an arrangement vertically or in parallel to the knitting needles.

We claim:

1. A method for detecting a broken needle and stopping the' knitting operation of a circular knitting machine comprising the steps of:

detecting the force on a knitting needle at the butt thereof by a stitch held thereon when said knitting needle is drawn in slightly during sliding and passing of the needle during knitting,

measuring the force detected by said detecting step,

converting the measured force into an electrical signal, and

actuating a switch of the driving electrical source of said knitting machine for shutting 011 said driving electrical source in response to said electrical signal when the force on said knitting needle is not detected by said detecting step.

2. An apparatus for detecting a broken needle and stopping the knitting operation of a circular knitting machine comprising:

means for detecting the force by a yarn on the needle,

said means disposed in a position where the knitting needle is drawn in slightly while the butt thereof is sliding and passing during knitting,

a force measuring strain gauge means for measuring the force detected by said detecting means,

means for converting the measured force into an electrical signal, and

circuit means for shutting off said circular knitting machine when the force on a knitting needle is zero.

3. The apparatus, as set forth in claim 1, further comprising:

a stitch cam for said knitting needles, and said detecting means being disposed in said stitch cam.

4. The apparatus, as set forth in claim 2, further comprising:

an auxiliary head set in front of said detecting means,

said needle including a butt,

said auxiliary head and detecting means disposed in the sliding path of said butt whereby after the position of the butt is corrected by said auxiliary head, said butt slides and passes by said detecting means.

References Cited UNITED STATES PATENTS 2,760,363 8/1956 Van Alen et a1 66157 FOREIGN PATENTS 1,149,129 2/ 1954 Germany.

785,651 10/1957 Great Britain.

MERVIN STEIN, Primary Examiner. 

